Aetna CEO Mark Bertolini on what's wrong with exchanges

Aenta CEO Mark Bertolini thinks health insurance exchanges have "so much wrong" with them since enrollment opened that it could take up to three years to resolve the issues.

"There's so much wrong, you just don't know what's broken until you get a lot more of it fixed," he said on CNBC's "Squawk Box."

And since Aetna served as an alpha tester for the exchange system, Bertolini had insight into the amount of problems facing the online marketplace before enrollment began. "We were pretty nervous as we got further along," Bertolini said. "As they started missing deadlines, we were pretty convinced it was going to be a difficult launch."

He added that most of the exchange construction was "on the fly." For example, Bertolini said Aetna "didn't get code drops until the last month before the system went live."

These problems could have factored into Aetna's decision to reduce the number of exchanges in which it's participating. The insurer adjusted its expectations, with Bertolini saying it wants to take a measured approach to selling plans through the online marketplaces, FierceHealthPayer previously reported.

What's more, he fears the technical glitches associated with the exchange rollout of could cause fewer young adults to sign up for coverage. "I think the attention span of the younger generation in using technology is that if it doesn't work the first time, it's going to be pretty hard to get them back the second time," he said. "If the program blows up because people don't sign up, then the program's not going to move ahead ... all that well."